1. Field of the Invention
This invention relates generally to solid-state circuit interrupters and more specifically, to such circuit interrupters as are utilized in molded case and metal clad type circuit interrupters and as are capable of acting on a number of complex electrical parameters in order to protect the electrical conducting system and devices connected thereto. This invention further relates to such circuit interrupters that allow for system user interaction so that the number of electrical parameters can be easily and readily understood and responded to.
2. Description of the Prior Art
The solid-state circuit interrupter is being employed today for significantly more complex commercial and industrial applications than was the original circuit interrupter first introduced as a resettable replacement for a common fusing element. Additionally, with the recent explosion in the use and performance attributes of the microprocessor arts along with the coincident increasing cost advantage for such devices, the application of microprocessor teachings to the circuit interrupter field has brought a commensurate demand for more complex analysis, greater performance features, and easier interaction with the solid-state circuit interrupter while at the same time, maintaining or improving the cost factor for such circuit interrupters.
An existing microprocessor based solid-state circuit interrupter is disclosed in U.S. Pat. No. 4,331,997 issued to Engel and assigned to the same assignee as the present application. This device was able to apply microprocessor technology to existing circuit interrupters while maintaining the supervisory control over such factors as instantaneous protection, short delay protection, long delay protection and ground fault protection that were found on existing solid-state circuit interrupters such as those that utilized discrete or other integrated circuit electronic components. As examples of circuit interrupters utilizing discrete components, reference is now made to U.S. Pat. No. 3,590,326 issued to Watson on June 29, 1971 and U.S. Pat. No. 3,818,275 issued to Shimp on June 18, 1974. In addition, the microprocessor based circuit interrupter was able to incorporate display and input monitoring techniques that provided for more accurate and reliable interface and operation of the electrical distribution system on which the circuit interrupter was being utilized.
This processor based circuit interrupter also proved advantageous in energy management systems where it was necessary to configure the electrical distribution system to achieve maximum energy efficiency and a minimum circuit interruption to the system as a whole. It is well known in the field that in configuring an electrical distribution system, a main circuit interrupter which protects a line feeding a number of branch circuits each having a branch circuit interrupter disposed thereon, should have delay times assigned so that in the event of a fault in one of the branch circuits, the associated branch circuit interrupter would trip before the main circuit interrupter. In this manner, the entire electrical distribution system would not be interrupted by a fault condition in a branch circuit and, the device or devices which that branch circuit was feeding, would also be protected in a more timely manner. Still other zone interlocking conditions can be accommodated using similar design criteria as the above example.
The microprocessor based circuit interrupter also proved advantageous over existing circuit interrupters in the method of selecting and adjusting the tripping parameters. The electrical distribution system design was greatly simplified since it was no longer required that a trial-and-error approach to field timing the tripping parameters be performed.
This microprocessor based circuit interrupter though effective and certainly an advance over the then existing circuit interrupters, did have certain limitations that the present application addresses and overcomes. For instance, it would have been a great advantage to have a communication link tied to the microprocessor based circuit interrupter so that in working with an energy management system the circuit interrupter could be instructed from a remote location to perform various supervisory tasks such as, for example, a load shedding operation.
Another example of such a limitation can be found in the use of what is commonly referred to as an override circuit. The override circuit establishes the maximum withstand rating of the particular circuit interrupter; the withstand rating being the current limit which, if exceeded, would result in damage to the tripping mechanism such as welding of the contacts. Since the withstand rating can vary according to the tripping mechanism with which the circuit interrupter is being used, it can be appreciated that a number of different override protection circuits can be provided for any particular circuit interrupter. Recognizing also that there is a number of rating plug factors which can be selected for the particular circuit interrupter, it becomes evident that a significantly large number of possible combinations of override values and plug rating factors can be achieved. The consequence of providing for all combinations of override settings together with all possible plug rating factors is the requirement that a large inventory of different combination circuit interrupters be maintained.
If an attempt were made to incorporate the element which establishes the override setting into the plug rating element, there would still be a need to maintain a large inventory of rating plugs that would accomodate all the possible combinations of override settings and plug rating factors. Additionally, a cumbersome interlocking arrangement would be needed between the elements that establish the two variables to provide for multiple plug styles for each rating plug factor and for each override level.